This Australian Standard applies to gauge blocks of rectangular form in inch sizes up to 4 inches, and to the commoner types of accessories used with such gauges.Provision is made for gauges of four grades of accuracy, namely:-a. workshop gauges; b. inspection gauges; c. calibration gauges; d. reference gauges.Recommended sets of gauges are given in Appendix B.NOTE. Workshop and inspection sets of gauges normally include a pair of extra gauges usually of 0.1 in. length, known as 'protector slips.' These gauges are of the same material, general dimensions, and accuracy as the other gauges in the set and are customarily marked with the letter 'P' on the face opposite to that, which should be wrung to the end gauge of the size combination.Protector slips are also made of tungsten carbide or similar wear-resisting material and may be obtained in such material as separate accessories to gauge block sets.